Skin specific antibodies are demonstrable in sera and blister fluids of patients with pemphigus and bullous pemphigoid. In addition, bound immune globulins and complement are present in skin lesions of these patients. In dermatitis herpetiformis, IgA and complement localization has been noted in the skin of these patients. Complement, therefore, is implicated in all three diseases. The present investigations, therefore, are designed to answer the question: are these immunologic diseases mediated by the complement system? We therefore plan to: 1) examine sera, blister fluids and skin lesions of these patients for complement activation and immune complex formation, 2) isolate and identify the responsible antigens, and 3) develop reliable experimental animal model systems. Of particular interest would be the method of complement activation. A better understanding of the pathogenesis of these diseases would result from such studies.